In order to protect from damaging outer physical or chemical effects, it has been established that MEMS components (micro-(electro)-mechanical components should be encapsulated using a protective wafer, which may have cavities and through holes, in an appropriate wafer composite. It is usual to align the protective wafer on the wafer having the MEMS patterns, and to join them by established techniques, such as anodic bonding or seal glass bonding.
For optical MEMS components, in addition to the requirements described, on the cap wafer a transparent window over the cavity, having a high optical quality, is regularly required. A method for its production is described in German Patent Application No. DE 10 2009 045 541 A1. For the purpose of reducing interfering reflections at the border surfaces of the optically transparent window, thin anti-reflex coatings are applied onto such windows or these are inclined with respect to the MEMS component.
Inclined optical windows for occasional chips are described in European Patent No. EP 1 688 776 A1. Inclined windows especially for the design of wafers made of several layers are described in U.S. Published Patent Application No. 2007 0024549, and their production is explained. German Patent Application No. DE 10 2008 012 384 A 1 describes a cover for encapsulating microsystems, which includes a slantwise optical window, as well as a method for its production.